Transformer



Aug. 17 1926.

F. J. FISCHER TRANSFORIER Filed Jan. 2'7. 1925 T 8| thereto and connected for I correspon and2 show e delta connections of the pri- Patented Aug. 17, 1926 UNITED STATES PATENT OFFICE.

M2108 FISCHER, OF DRESDEN, GERMANY, ASSIGNOB TO THE STERZEL A. G., OF DRESDEN, GEBMANY FIRE KOCH &

rmsrommn.

Application Med January 87, 1925, Serial Rb. 5,078, and in Germany December 4, 1988.

There have been proposed various means for reducing the. no-load losses of a transformer at light loads. In particular it is known, in connection with three-phase 5 transformers, with which the present invention is concerned, to change over from a delta-connected systemused under full load conditions to a star-connected systemat lighter loads, this conversion from deltato '10 star-connected system, according to the arrangement proposed being both primary sided and 'secondary sided, that is, both the primary windings and "secondary windings being converted, from delta to star connecll tions.

In contradistinction therewith, in accord-' windings is always available, the star point so canbeusedastheneutralpointandcanalways be fully loaded.

A further advantage 'of the method in accordance with the invention is that atransform er built for operation according light loads may be connected in el wi other transformers under load.

As a further method of reducing the noload losses with lightly-loaded transformao ers,'the arrangement in series of otherwise parallely-disposed secondary winding sections' is known, but only 1n the form of double-star-connection in acertain sense. The known ent, however, has no a concern with a three-phase transformer and is not staror double-star-connectiom The-invention is illustrated in the accompanying drawing in which similar reference characters denote parts and in which Figs. 1

marv coils; Figs. 3 and 4 show the star connections of the primary coils; Figs. 5 and 6 show the star-connected subdivided secondary coils in which the sections are connected in parallel; Figs. 7 and 8 show the starconnected subdivided secondary coils in which the different sections are connected in series or double-star, and Fig. 9 illustrates the adjustable switch in the position for full load.

Referring first to Figs. 1-4, U, V and W are the receiving ends of the primary coils and X, Y and Z the corresponding opposite ends thereof. If U be connected with Z, V with X and W withY, the rimary coils are delta-connected-for full fbad, as indicated in Fig. 2. If X, Y and Z of the pri- -mary coils be connected together, then the delta connection is changed to star connection for low load, as shown in 3 and 4.

Referring now to Figs. 5-8 the ends of someof the sectionsof the secon coils are 11, 0,10 and this opposite ends thereof av, 3 z, and the starting ends of the other sections of the coils are u, 'v, w and their corresponding opposite ends at, y, a. now u be connectedwith u, v withv and w with w, a; with w, y with a with a, and m, y and s are connected shown in .Fig. 5, the two sections of the secondary coils on each leg are star-connected .for full load, as shown in Fig.6, the star point 0 being used as the neutral int. If, on the other hand, u be conn with "v' and w, a: with y, y with a andz with coil on another :12, the one section of a second one leg is connected in series wit section 'of the secondary coil on another leg. This connection used for low load I term do'uble-star-connection, the same being indicated in Fig. 8. v I

The adjustable switch shown in Fig. 9 illustrates the method of operation.

As shown, on the common spindle 1, are

together, as

mounted double or multiple contact knives 2', 2",for the primary system, and 3', 3'-' for the secondary system, the contacts 4 of the primary system and 5 of the secondary system being arranged opposite one another in series, in such manner that on rotation of the spindle through 180 the change over from the connections for full-load condition (indicated in Fig. 9) to those for lowload condition is efiected.

What I claim is v A method of reducing the no-load losses on three-phase transformers secondary continuously having the winding subdivided in sections star-connected, consisting in changing the primary windings from delta connections at full load to star connections 10 at low load and simultaneously changing the secondary windings from parallel at full load to series or doube-star at low load.

In testimony whereof I afiix my signature.

FRANZ JOSEF FISCHER. 

